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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 300 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 67° and 37°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 5 cm, 8 cm and 5 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  10. 10.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  11. 11.The two interior opposite angles of a triangle are 28° and 34°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 55° and angle B = 61°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 27° and angle B = 41°. What is angle C (in degrees)?
  18. 18.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  19. 19.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 8 cm and 6 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 30° and 79°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 6 cm, 10 cm and 12 cm? (a) Yes (b) No
  32. 32.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 97° and angle B = 57°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 67° and angle B = 69°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 50° and angle B = 32°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 67° and angle B = 55°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 6 cm, 7 cm and 11 cm? (a) Yes (b) No

Answer key

  1. 28
  2. 20
  3. 104
  4. Yes
  5. 30
  6. 65
  7. 26
  8. 56
  9. 52
  10. 12
  11. 62
  12. 23
  13. 64
  14. 14
  15. 45
  16. 75
  17. 112
  18. 15
  19. 130
  20. 50
  21. 48
  22. 72
  23. 75
  24. 50
  25. 32
  26. Yes
  27. 128
  28. 39
  29. 26
  30. 109
  31. Yes
  32. 25
  33. 26
  34. 44
  35. 25
  36. 44
  37. 98
  38. 90
  39. 58
  40. Yes

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